Influence of visual field threshold fluctuation on high resolution perimetry with 0.5-degree interval

Abstract

Purpose: It is well known that visual field threshold can fluctuate. The fluctuation is small where the visual field threshold is small, and the fluctuation is large where it is large. The visual field threshold also fluctuates at localized areas such as scotoma. We performed an observational clinical study using high resolution perimetry with 0.5-degree interval to investigate the factors for the visual field threshold fluctuation.

Methods: Sixteen eyes of 16 patients with glaucoma (mean age: 63.1 ± 5.9) were studied. Octopus 900 Custom test program was used with target size III and background luminance of 31.4 asb to measure the sensitivity on the upper temporal meridian of 45 degrees from the fixation point to the eccentricity of 30 degrees with the interval of 0.5 degrees. The sensitivity was evaluated 3 times at each point. Visual field threshold was determined by computing the mean sensitivity of the 3 repeats at each test point. The standard deviation was defined as test- retest SD. In order to evaluate local visual field threshold fluctuation at scotoma or else, we also computed Spatial SD along each sample line using a moving window of between 3 and 20 points wide.<br /> In addition, we computed the independent variable Spatial Interaction (SI) multiplying visual field threshold by Spatial SD at each point. Using univariate correlation analysis, associations were examined between test- retest SD and visual field threshold, Spatial SD, SI, and the eccentricity. We also did a multivariate regression analysis to look for the independent factors that best determined test- retest SD.

Results: Univariate correlation analysis revealed test- retest SD was significantly correlated (p < 0.002) with the eccentricity, visual field threshold, Spatial SD, and SI. Test- retest SD showed strongest correlation with visual field threshold (p < 0.002; r = -0.342) and Spatial SD (p < 0.002; r = 0.452). Multivariate regression analysis showed test- retest SD was affected by visual field threshold (p < 0.01; t-value 5.05) and Spatial SD (p < 0.01; t-value 12.5).

Conclusions: Visual field threshold fluctuation was mostly affected by visual field threshold and Spatial SD.